To estimate design floods for hydraulic structures, statistical methods has been used in the analysis of rainfall data. However, due to the lack of rainfall data in some regions, it is difficult to apply the statistical methods for estimation of design rainfall. In addition, increased uncertainty of design rainfall arising from the limited rainfall data can become an important factor for determining the design floods. The main objective of this study was to assess the uncertainty of the future design floods under RCP (representative concentration pathways) scenarios using a bootstrap technique. The technique was used in this study to quantify the uncertainty in the estimation of the future design floods. The Yongdang watershed in South Korea, 2,873 ha in size, was selected as the study area. The study results showed that the standard errors of the basin of Yongdang reservoir were calculated as 2.0~6.9 % of probable rainfall. The standard errors of RCP4.5 scenario were higher than the standard errors of RCP8.5 scenario. As the results of estimation of design flood, the ranges of peak flows considered uncertainty were 2.3~7.1 %, and were different each duration and scenario. This study might be expected to be used as one of guidelines to consider when designing hydraulic structures.

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A number of the Bronze Age dwelling sites have been found and excavated in the Yoodoocheon, Onyangcheon and Baekseokdong basins. Two basins are located near Asan and Onyan in the Chungnam Province of South Korea. Baekseokdong is located in Cheonan, Chungnam. 207 dwelling sites are concentrated around the area of 1.3 ㎢ in the Baekseokdong. 177 dwelling sites are sparse and distributed over the area of 1.3 ㎢ in the Yongdoocheon and Onyangcheon basins. Most of the Bronze Age dwelling sites in those areas located on the hill. The hills have similar geomorphological environments except for slight differences in geological faces. This study analyzes geomorphological environments of the high-density residential zone of the Bronze Age in the Yoodoocheon and the Onyangcheon basins, and then compares them with the results in Baekseokdong. Study results show that high-density residential zone consists mainly of specific micro-landforms such as the Crest slope, the Crest flat and the Upper side slope, and southeast-facing aspect. A lot of Gentle slope lands were distributed in terms of terrain slope but it is far from specific geomorphological environments. This is not weighted in specific value. Our results show that the geomorphological characteristic derived from this study is major considerations to develop dwelling sites in the Bronze Age. This can be useful to discover the possible dwelling sites over other Chungnam hill regions.

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